CS4 Now is asking for serial number again (after years of use) and doesn't recognize that which came with the software?

I have CS4 Creative Suite.  Was running without problem. Mostly using photoshop and the Acrobat Pro.  Photoshop seems to still be working but Acrobat is asking for serial number.  It won't seem to accept the original serial number.  This is a purchased copy with valid numbers.  I reinstalled with no change.  This is a new computer and I was sure to uninstall all my software on this prior to new computer.  I haven not had any problems for a year and now I can't even view a pdf file.